1. Field of the Invention
Exemplary embodiments of the present invention relate to a recliner for a vehicle seat, and more particularly, to a recliner for a vehicle seat capable of maintaining lubrication action by configuring a lubricating oil supply portion capable of supplying a lubricating substance to any one of respective contact surfaces between a socket, a bush, wedge blocks, and a cam sleeve which are operatively pressed against each other.
2. Description of the Related Art
In general, a vehicle is equipped with a seat back, which is pivotable relative to a seat cushion by forming the seat back as a hinge structure, and a recliner allowing the seat back to be mutually switched from a locked state of being fixed to the seat cushion at a certain angle to an unlocked state of being pivotable relative to the seat cushion. That is, a passenger may adjust an angle of the seat back according to the body form or convenience thereof by operation of the recliner.
Such recliners are classified into a lever type recliner in which, when an operation lever is operated, a recliner is unlocked so that a seat back is pushed by a passenger's back to adjust an angle of the seat back, and a rotary type recliner which adjusts an angle of a seat back by turning an operation knob in the form of a dial.
Among the recliners, the rotary type recliner is disclosed in Japanese Patent Laid-Open Publication No. 2010-253101 (Patent Document 1). FIG. 1 shows an example of a conventional rotary type recliner.
As shown in the drawing, a conventional recliner 10 includes a shaft 11, an external gear bracket 12, an internal gear bracket 13, a socket 14, a bush 15, a plate cover 16, a guide ring 17, and a power transmission unit 20.
The external gear bracket 12 is formed, at a center thereof, with a fitting hole 12a, while being formed, at an inside surface thereof, with an external gear 12b. 
The internal gear bracket 13 is formed, at a center thereof, with a central protrusion 13a protruding therefrom, while being formed, at a circumferential surface thereof, with an internal gear 13b which selectively engages with the external gear 12b. The internal gear 13b has the number of gear teeth less than the number of those of the external gear 12b. 
The socket 14 is formed, at a center thereof, with a coupling hole 14a through which the shaft 11 passes so that the shaft 11 is spline-coupled to the socket 14. The socket 14 is formed, at one side surface thereof, with a socket protrusion 14b protruding therefrom so that the socket protrusion 14b is inserted into the central protrusion 13a of the internal bracket 13. The socket 14 is provided with a spring protrusion 14d protruding in a direction opposite to the socket protrusion 14b. 
The bush 15 is fitted and coupled to the fitting hole 12a of the external gear bracket 12.
The power transmission unit 20 rotates the external gear bracket 12 relative to the internal gear bracket 13. The power transmission unit 20 includes a cam sleeve 22 surrounding a portion of an outer peripheral surface of the central protrusion 13a, a pair of wedge blocks 21 provided between the cam sleeve 22 and the bush 15, and a wedge spring 23 which is fitted and installed between the pair of wedge blocks 21 by bending both ends of the wedge spring 23 so as to apply force for outwardly spreading the wedge blocks 21.
The cam sleeve 22 has a semicircular shape and is configured such that an inner peripheral surface thereof surrounds a portion of the outer peripheral surface of the central protrusion 13a. 
The pair of wedge blocks 21 is configured to face each other and to be spaced apart from each other at one end portions thereof. The other end portions of the wedge blocks 21 are configured to be bent and press an end portion of the cam sleeve 22 during operation of the recliner.
The plate cover 16 encloses one surface (a front surface in FIG. 1) of the external gear bracket 12 so as to prevent decoupling of the socket 14 and the power transmission unit 20 therefrom.
The guide ring 17 surrounds the external gear bracket 12, the internal gear bracket 13, and an outer peripheral surface of the plate cover 16 so that they are integrally coupled.
In the conventional recliner 10, the shaft 11 is rotated by actuation force of a lever or a motor and the socket 14 coupled to the shaft 14 is also rotated. In this case, the socket 14 rotates the cam sleeve 22 together with the wedge blocks 21, and the rotation of the wedge blocks 21 causes a change in position of an engagement section due to a difference of the number of gear teeth between the external gear 12b and the internal gear 13b. Accordingly, an angle of a seat back is adjusted by the change in position of the engagement section.
However, operation of the conventional recliner 10 applies a load to an inner peripheral surface of the bush 15 and the outer peripheral surface of the central protrusion 13a of the internal gear bracket 13 coming into contact with the cam sleeve 22 and the wedge blocks 21 rotated by the socket 14 during the operation of the conventional recliner 10.
In this case, there is a problem in that noise is generated since actuation force is increased due to an increase of friction force between the outer peripheral surface of the central protrusion 13a and the cam sleeve 22 and between the inner peripheral surface of the bush 15 and the wedge blocks 21.
In addition, there is a problem in that durability of the recliner is deteriorated since the outer peripheral surface of the central protrusion 13a and the inner peripheral surface of the bush 15 are worn out by friction force generated between the outer peripheral surface of the central protrusion 13a and the cam sleeve 22 and between the inner peripheral surface of the bush 15 and the wedge blocks 21.
[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-253101